1. Field of the Invention
Embodiments of the present invention relate to a separate measuring device used to define the angular relationship between a flat or curved peripheral surface such as an abrasive belt or a grinding wheel and another peripheral surface or tool such as a grinding platform, a tool rest, or a woodworking tool.
2. Description of Related Art
Angle gauges are commonly used to determine the angle between a grinder or belt sander and a tool rest when sharpening metal tools, or between any two surfaces when the angle between the surfaces needs to be determined with precision. The following discussion will focus on sharpening woodworking tools; however, this invention is not limited to sharpening tools.
Sharpening woodworking tools is typically accomplished by resting the tool on the grinder platform such that the longitudinal axis of the tool is parallel to the plane created by the top of the platform surface; the tool is then pressed toward the abrasive surface by hand. Employing this hand-held method requires a tool platform that adequately supports the workpiece as well as having the platform set to the correct angle and position to obtain the desired angle of the sharpened edge of the workpiece.
Longer woodworking tools, such as woodturning tools, make use of a conventional grinding platform inconvenient because the center of gravity of the woodturning tool is typically not resting on the platform; because of this, it is common to secure the rear of woodturning tools with an extensible work rest such that the height and distance of the rear of the workpiece from the grinding surface determines the angle of the intersection of the edge to be sharpened with the surface of the grinder.
It is fairly common for grinder platforms to incorporate a fixture to assist with making angular measurements between the grinding platform and the abrasive surface. A problem common to such fixtures is that they measure the angle of surface of the platform in relation to the grinder, not the angle of the tip the workpiece placed upon the grinding platform, which is where the true angle of the edge of the workpiece is created. The angle created on the tip of the workpiece becomes increasing inaccurate with grinding wheels because they vary in diameter over time due to wear and attrition while a fixed tool rest typically does not compensate for this; additionally, platform fixtures cannot be used to gauge the angle on more than one grinder.
There are several methods commonly used to determining the variable angular relationship between a curved grinding surface and a grinding platform that do not incorporate the use of a fixed grinder platform angle gauge. Common methods include: simply grinding the workpiece and measuring the resulting angle of the sharpened workpiece; preparing blocks of wood, called jigs, with the desired angles preset on one of their edges; placing a protractor on the grinding platform and along the side of the grinding wheel; or placing a digital angle gauge on the platform. All of these methods can be adapted to work with longer workpieces.
While the proceeding methods work, they are all slow: the trial and error of grinding first and measuring later is time consuming; as is sorting through numerous pre-cut jigs to find the right angle; while placing a protractor along the side of a grinding wheel requires time to place it in the correct location; and digital angle gauges must either be preset to the right angle or the tool rest must be held carefully while the angle of the rest is set.
Embodiments of the present invention overcomes this shortcoming by allowing most of the commonly used angles needed for sharpening woodworking tools to be set by glancing at the angle gauge, placing it on the tool rest, and adjusting the tool rest snugly to the angle gauge without sorting through jigs, bending over to view and angle, or setting an angle on the gauge. Additionally, unlike the commonly used methods, the present invention incorporates angular compensation for workpiece thickness and variations in grinding wheel diameter. This angle gauge can also be attached to a holder that allows for accurate measurement of the angle of longer workpieces where platform tool rests cannot be used.